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When an atom, ion, or molecule moves from a higher-energy state to a lower-energy state it emits photons with energies equal to the difference in energy between the two states. The result is an emission spectrum that shows the intensity of emission as a function of wavelength.
The main difference between emission and absorption spectra is that an emission spectrum has different coloured lines in the spectrum, whereas an absorption spectrum has dark-coloured lines in the spectrum.
Let’s go back to simple absorption and emission spectra. We can use a star’s absorption spectrum to figure out what elements it is made of based on the colors of light it absorbs. We can use a glowing nebula’s emission spectrum to figure out what gases it is made of based on the colors it emits.
This spectrum of radiation emitted by electrons in the excited atoms or molecules is known as an emission spectrum. Absorption Spectrum. We observe that when a ray of white light falls on a prism it experiences refraction twice.
Atomic spectra refer to the unique patterns of light emitted or absorbed by atoms when their electrons move between different energy levels. When an electron jumps from a higher energy level to a lower one, it emits light; when it jumps from a lower to a higher level, it absorbs light.
Absorption is the process that consumes a photon and puts the atom or molecule in an excited state. Emission is the process that creates a photon and takes the the atom or molecule in an excited state back to the ground state. The Emission Spectra of H, He and Hg.
Atoms can be excited when irradiated, which creates an absorption spectrum. When an atom is excited, the valence electron moves up an energy level. The energies of the various stationary states, or restricted orbits, can then be determined by these emission lines.
Atomic Absorption Spectra. In addition to emission studies, chemists will also use atomic absorption to identify and quantify. Noting the energy changes from ground to excited states, chemists can obtain another type of discontinuous spectrum (see image below).
An absorption spectrum occurs when light passes through a cold, dilute gas and atoms in the gas absorb at characteristic frequencies; since the re-emitted light is unlikely to be emitted in the same direction as the absorbed photon, this gives rise to dark lines (absence of light) in the spectrum.
Simplified illustration of absorption and emission spectra. Every element has a unique set of absorption and emission lines, or spectral signature. The absorption and emission spectra of each element are inverses of each other. The wavelengths of a particular element’s absorption lines are the same as the wavelengths of its emission lines.